This relates generally to displays, and more particularly, to displays with backlights.
Displays such as liquid crystal displays and other displays sometimes include backlight units. A backlight unit may include an array of light-emitting diodes and a backlight control integrated circuit (sometimes referred to as a backlight driver) that directly controls the array of light-emitting diodes. Displays with backlight units may be incorporated into an electronic device such as a computer or cellular telephone or may be implemented as stand-alone units.
There is an increasing demand for electronic devices such as portable computers to be capable of supporting both a non-movie mode and a movie mode. For example, a laptop computer may be operated in the non-movie mode when a user is using the laptop computer to give a presentation or to run a text-editing application. The laptop computer may also be operated in the movie mode when the user is using the laptop computer to watch a movie. In either mode, the backlight unit is used to output a fixed backlight level such that the intensity of light generated by the light-emitting diodes remains constant from frame to frame.
Implementing the fixed backlight level in the movie mode, however, consumes an excessive amount of power. Consider, for example, a scenario in which two consecutive frames in the movie mode transition from a bright scene to a dark scene. In this example, the backlight unit would output a fixed backlight level in both the bright scene and the dark scene. Display pixels in the liquid crystal display contain thin-film transistors and electrodes for applying electric fields to the liquid crystal material. The strength of the electric field in each display pixel controls the polarization state of the liquid crystal material and thereby adjusts the brightness of each display pixel (i.e., changes in brightness from frame to frame is adjusted via control of the liquid crystal material without any adjustment to the backlight level).
It would therefore be desirable to be able to provide improved ways in which to control the brightness level of the display in the different display modes.